$OpenBSD: patch-pixmap_c,v 1.1 2017/04/18 21:13:03 espie Exp $
--- pixmap.c.orig	Tue Apr 18 07:59:36 2017
+++ pixmap.c	Tue Apr 18 09:43:55 2017
@@ -395,6 +395,9 @@ pixmap_index (int x, int y)
 {
     return y*pixmap_width + x;
 }
+
+/* also mark it as extern for C99 */
+extern int pixmap_index(int, int);
 #endif
 
 int 
